A standard 9-pin or 3-pin cable depending on your STB model.
To use the tool, you must establish a physical connection between your PC and the STB: stb upgrade tool ver 40 2 link
[LINK] Negotiating with 47 peer STBs... [LINK] Consensus reached. Proceeding. [STATUS] Upgrading... 2%... 7%... A standard 9-pin or 3-pin cable depending on your STB model
STB Release Upgrade STB Release Backup Via RS 232 Port stb upgrade tool ver 40 2 link